1. Field of the Invention
The present invention relates to an electronic apparatus having an antenna for receiving radio waves by an antenna coil.
2. Description of the Prior Art
In a background art, there has been developed an electronic apparatus having an antenna of a radio wave timepiece, a portable telephone or the like.
According to the electronic apparatus having an antenna of the background art, there is used an antenna apparatus for receiving radio waves by winding an antenna coil around an antenna magnetic core member referred to as a core.
For example, according to radio wave timepieces disclosed in Patent Reference 1, Patent Reference 2, in order to deal with frequencies or the like of a plurality of different long standard radio waves, there is disclosed an antenna having a plurality of coils at a core, changing inductances thereof by switching by a switch to thereby enable to change tuning frequencies.
Although a receiving sensitivity of an antenna is influenced by a volume of a core and a coil volume, when a plurality of coils are provided as in the background art, there is needed a nonwinding portion for connecting antennas disposed at both ends of the core. Therefore, in order to provide a predetermined necessary coil volume, it is necessary to increase turn numbers of the respective coils by enlarging the core to pose a problem that a size thereof is enlarged.
This poses a serious problem particularly in a portable electronic apparatus having an antenna of a portable radio wave timepiece, a portable telephone or the like requested to be downsized.
Further, although Patent References 1, 2, mentioned above, disclose a radio wave timepiece having a plurality of tuning circuits, the tuning circuits are for tuning to frequencies different from each other (for example, 40 kHz and 60 kHz) and are not for tuning to the same frequency.
<Patent Reference 1> JP-A-2003-60520
<Patent Reference 2> Japanese Patent Publication No. 3526874
It is a problem of the invention to provide an electronic apparatus having an antenna having a plurality of antenna coils which can be downsized.